From 7b3cd710858d4d7d2af7d8f706870352458140d0 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Fri, 28 Jan 2022 13:54:06 +0100
Subject: [PATCH] fixed improper optimization of word<<8 and word>>8

---
 .../prog8/optimizer/ExpressionSimplifier.kt   | 12 ++--------
 docs/source/todo.rst                          |  2 --
 examples/test.p8                              | 22 ++++++++++---------
 3 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
index e9fa04632..d3f17dab0 100644
--- a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
+++ b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
@@ -680,11 +680,8 @@ class ExpressionSimplifier(private val program: Program, private val errors: IEr
             DataType.UWORD, DataType.WORD -> {
                 if (amount >= 16) {
                     return NumericLiteralValue(targetDt, 0.0, expr.position)
-                } else if (amount >= 8) {
+                } else if (amount > 8) {
                     val lsb = FunctionCallExpression(IdentifierReference(listOf("lsb"), expr.position), mutableListOf(expr.left), expr.position)
-                    if (amount == 8) {
-                        return FunctionCallExpression(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(lsb, NumericLiteralValue.optimalInteger(0, expr.position)), expr.position)
-                    }
                     val shifted = BinaryExpression(lsb, "<<", NumericLiteralValue.optimalInteger(amount - 8, expr.position), expr.position)
                     return FunctionCallExpression(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(shifted, NumericLiteralValue.optimalInteger(0, expr.position)), expr.position)
                 }
@@ -722,13 +719,8 @@ class ExpressionSimplifier(private val program: Program, private val errors: IEr
                 if (amount >= 16) {
                     return NumericLiteralValue.optimalInteger(0, expr.position)
                 }
-                else if (amount >= 8) {
+                else if (amount > 8) {
                     val msb = FunctionCallExpression(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position)
-                    if (amount == 8) {
-                        // mkword(0, msb(v))
-                        val zero = NumericLiteralValue(DataType.UBYTE, 0.0, expr.position)
-                        return FunctionCallExpression(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(zero, msb), expr.position)
-                    }
                     return TypecastExpression(BinaryExpression(msb, ">>", NumericLiteralValue.optimalInteger(amount - 8, expr.position), expr.position), DataType.UWORD, true, expr.position)
                 }
             }
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 7af4a0d97..b02846815 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,8 +3,6 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-- fix optimization of w >>= 8 , it generates bad code when opt=on, ok when opt=off
-- fix w <<= 8 generates weird code with pha/pla in it when opt=on, ok when opt=off
 - optimize  w=msb(w)  =>  w >>=8,  w=lsb(w) ==> w &= $00ff
 
 fix the value of ww being wrong (with optimizations enabled) in :
diff --git a/examples/test.p8 b/examples/test.p8
index c2871da29..050046cf2 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,22 +4,24 @@
 main {
     sub start() {
         uword @shared xx=$ea31
-        xx &= $00ff
+        ;xx &= $00ff
         ;xx = lsb(xx)
-        txt.print_uwhex(xx, true)
-        xx = $ea31
-        xx &= $ff00
+        ;txt.print_uwhex(xx, true)
+        ;xx = $ea31
+        ;xx &= $ff00
         ; xx = msb(xx)
 ;        %asm {{
 ;            nop
 ;            nop
 ;        }}
-;        xx >>= 8
-;        %asm {{
-;            nop
-;            nop
-;        }}
-;        xx <<= 8
+        xx >>= 8
+        %asm {{
+           nop
+        }}
+        xx <<= 8
+        %asm {{
+           nop
+        }}
         txt.print_uwhex(xx, true)
     }
 }